[m-users.] adding grades (Sean Charles (emacstheviking))

[Fabrice Nicol]

Another option is to use Linux containers rather than building native.

I've uploaded a couple of images with C-based grades to Docker Hub.

I'll be including java grades within a week.

Docker pushes are going to be automated using GitHub workflows, on a 
weekday basis, so there is going to be a rolling release of ROTDS built 
with as many grades as can be (hopefully with C# too).

Tests show that running Mercury within Linux containers only incurs 
minimal overhead and may be even faster than running native builds on 
Windows.

Fabrice